1. Field of the Invention
The present invention relates to a disk storage subsystem with multiple configurable interfaces used as mass storage for a computer system.
2. Description of Related Art
Mass storage applications for computers require more and more storage capacity and greater protection of the stored data (no loss of data as a result of a failure). Added to this is a concern for availability, the user being in need of highly reliable systems capable of operating continuously, even when maintenance of the systems is necessary.
There are two types of subsystems currently offered: the subsystems JBOD (Just a Bunch Of Disks) or RAID (Redundant Array of Inexpensive Disks). The JBOD (or direct disk attachment) subsystems are the simplest and the least expensive. They require only a small computer system interface (SCSI) adapter board to connect up to 4 6-disk drawers to host systems. It is possible, through the operating system, to produce duplications (mirroring) from one disk to another, and hence to secure the data so as to be protected against a disk failure.
The drawback of these systems is that the configurations are fixed (2 SCSI interfaces with a maximum of 12 disks) and therefore do not cover all the users"" needs. These systems do offer good protection of the data, because of the mirroring, but in case of a defect, for example of an element of the adapter board, the subsystem is no longer operational.
RAID systems can comprise two controllers, one of which makes it possible, in case of a failure of the other, to guarantee the correct operation of the disk storage subsystem, for example by connecting a first controller with the host and the second controller with the same host, but using different connections.
RAID subsystems are very high-cost due to the costs of the controllers and the cache memory required, and in some cases their performance is disappointing as compared to disks used in the conventional way. Moreover, the number of configurations is limited.
The object of the present invention is to eliminate the drawbacks of the prior art by offering a high-performance JBOD subsystem with very high availability, making it possible to protect a large volume of data, and allowing a wide choice of possible operating configurations.
This object is achieved by the fact that the disk storage subsystem with multiple configurable interfaces is characterized in that it comprises at least one interface adapter board, at least one drawer, each comprising a plurality of disks, each drawer being connected to an adapter board by SCSI disk interfaces, a first adapter board comprising a switch for modifying the addressing system of the disks of at least one drawer, the adapter board or boards each comprising two independent single-ended/differential-ended SE/DE interface converters, each SE/DE converter being connected to a drawer and fed by either of two direct current/direct current DC/DC converters of the adapter board, and two external SCSI connectors being connected to each SE/DE converter.
According to another characteristic, the switch is a hardware switch of the dual in-line switch type or a software switch.
According to another characteristic, the switch adds a constant value to the addresses of the disks of two drawers, this value preferably being equal to 8.
According to another characteristic, the SCSI interfaces that connect the drawers of disks to the controller card are of the single-ended SE type.
According to another characteristic, the SCSI interfaces that connect the adapter board to the host systems are of the differential-ended DE type.
According to another characteristic, each SE/DE converter is connected by a V connection to two connectors accessible to the outside of the subsystem for connecting either line terminators or bus adapters of a host machine.
According to another characteristic, each of the direct current/direct current DC/DC converters of the blocks of SE/DE converters distributes a voltage to the two SE/DE converters of the corresponding blocks by means of an xe2x80x9cwired OR.xe2x80x9d
According to another characteristic, the adapter board comprises a daughterboard, this daughterboard making it possible, in a first position, to connect the adapter board to two given disk drawers, and in a second position, to connect the adapter board to two drawers of disks different from those of the first position.
According to another characteristic, a link joins two connectors of two SE/DE converters, thus producing a chaining of two drawers of disks.
According to another characteristic, the SCSI disk interfaces connecting the drawers of disks and/or the SCSI disk interfaces connecting the adapter board or boards to the host systems are the Ultra/Vide type and hence support a maximum data rate of 40 megabytes/s.
According to another characteristic, the line terminators that are not located in the disk drawers are incorporated into each daughterboard of each associated adapter board.